This invention relates to an improved process for the manufacture of thianthrene compounds. Thianthrene and substituted compounds are useful in a variety of chemical processes, for example, as chemical intermediates in the preparation of dyestuffs such as thianthrene vat dyes. In addition, various thianthrene compounds are useful plasticizers, pesticides, and flameproofing agents. Recently it has been found that thianthrene compounds having electron withdrawing substituents such as halogens, on the aromatic nuclei thereof are especially useful as components of catalyst systems for the directed nuclear chlorination of alkylbenzenes. Although thianthrene compounds have been known for many years, little effort has been directed toward the development of a process suitable for commercial manufacture.
One laboratory method for the preparation of thianthrene compounds comprises the reaction of a benzene compound with sulfur monochloride in the presence of aluminum chloride. The reaction product is a thianthrene compound-aluminum chloride complex. The thianthrene compound may then be recovered from the aluminum chloride complex by treatment with iced hydrochloric acid followed by steam distillation and washing with a suitable solvent.
It is an object of the present invention to provide a process for the production and recovery of thianthrene based products which is direct and simple and which is adaptable to large scale commercial operations. A further object is to provide a method whereby a high purity thianthrene product may be produced in high yields. A still further object is to provide an improved process for the recovery of thianthrene compounds from a thianthrene compound-aluminum chloride complex.